Distribution and ecological risk assessment of arsenic and some trace elements in soil of different land use types, Tianba Town, China

In this study, the contents of chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), mercury (Hg), cadmium (Cd) and lead (Pb) in soils of different land use types in Tianba Town, southwest China, were studied to evaluate soil pollution, along with the potential ecological risk index (PERI), and its spatial distribution. A total of 2283 samples were collected from 761 sampling sites. After acid depletion, the contents of Pb, Cd, Cu, Cr, Zn, Hg, As and Ni were analyzed by inductively coupled plasma mass spectrometry. Principal component analysis (PCA), correlation analysis, cluster analysis, the Nemerow comprehensive pollution index and potential ecological risk were used to evaluate the source and degree of soil pollution, and the spatial distribution of soil elements was plotted using the Kriging interpolation technique with ArcGIS software. The results show that the average contents of Cr, Ni, Cu, Zn, As, Hg, Cd and Pb were 84.46, 39.50, 33.94, 96.92, 8.16, 56.90, 0.27 and 54.80 mg/kg, respectively. The contents of As and Cd were close to the background values, while the contents of Ni, Cr, Cu, Zn and Hg were higher than the background values. Based on PCA and HCA, soil pollution mainly comes from three different sources, and different land uses have different pollution degrees to some extent. The pollution index values of Cr, Ni, Cu, Zn, As, Hg, Cd and Pb were 1.22, 1.31, 1.06, 1.15, 0.80, 1.50, 3.51 and 1.76, respectively. The average comprehensive pollution load index was 2.71, indicating that the soil in the study area was moderately polluted. The mean PERI value was 197.65, indicating that the soil in the study area exhibited a severe potential ecological risk level. The spatial distribution of element content shows that Cd (55.00) and Cu (51.12) have high spatial variability. Furthermore, the study area shows that traffic land and forest land are at strong ecological risk, while grassland, cultivated land and construction land are at severe ecological risk. However, in the long term, Cd may accumulate in soil due to its release into the environment due to human activities. Therefore, controlling the emission of harmful compounds is recommended, especially those related to human activities in transportation land and woodland.